Bio101 Exam 3 - 10/30/26

What are the general functions of the plasma membrane?

Forms an external boundary around all animal cells
Creates a barrier that limits entry & exit of materials
Mediates transport of materials into/out of the cell
Interacts with the environment & responds to signal molecules/other external stimuli, then releases signals back into the environment

What is the structure of the plasma membrane based on?

Phospholipid bilayers

What does the amphiphilic nature of the bilayers do to the arrangement?

Spontaneously arranges the heads outward and tails inward

How does the plasma membrane behave at 37℃ (our body temperature)?

Like a fluid - phospholipids & molecules can move within it

What does the fluidity of the membrane depend on?

Temperature, phospholipid structure, and membrane composition

Molecules move more at _____ temperatures?

Higher

What type of membrane do organisms seek to create?

One that is fluid enough for movement yet rigid enough for integrity

How do mammals maintain fluidity in their membranes?

They try to keep a high body temperature

How do other living things maintain fluidity in their membrane?

By adjusting aspects of their membranes

The bonds between hydrocarbon tails can be either _____ or _____?

Single or double

What does a single bond mean?

Saturated

What does one or more double bonds mean?

Unsaturated

Which hydrocarbon tail (saturated or unsaturated) increases membrane fluidity?

Unsaturated

What other type of lipid does the membrane contain?

Steroids

What is the effect of high temperature of cholesterol in the plasma membrane?

Decreased fluidity

What is the effect of low temperature of cholesterol in the plasma membrane?

Increased fluidity

What do proteins do in the plasma membrane?

Mediate transport into/out of the cell
Interact with the environment
Transmit external signals into the interior of the cell

What type of proteins cross the membrane?

Integral/trans membrane proteins

What type of proteins do not cross the membrane?

Peripheral proteins

What forms the basic structure of the membrane create its fluid consistency?

Lipids

What carry out many of the membrane’s functions?

Proteins

How is molecular movement typically carried out?

Totally randomly

The phospholipid-based membrane is selectively permeable, meaning:

Only certain molecules can pass through freely without help

Only _____, _____ _____ molecules can easily pass through the plasma membrane.

Small, uncharged nonpolar

What is diffusion?

Movement in the direction of the concentration gradient

Does diffusion require energy?

No, it is driven by random molecule movement

What is free/passive diffusion and what molecules use it?

Small, nonpolar charged molecules that can freely cross the plasma membrane

What is facilitated diffusion and what molecules use it?

Polar uncharged molecules that must use a transport protein to cross the membrane

What are two types of protein that can be used for facilitated diffusion and how do they help?

Channel proteins - provide hydrophilic tunnel for solutes to pass through
Carrier proteins - bind solute to one side of the membrane and release it to the other side

What are examples of molecules that go through facilitated diffusion?

Water, glucose, and charged ions

How is equilibrium reached?

When molecules gradually distribute themselves equally throughout a given space

What is osmosis?

The facilitated diffusion of water

What is Aquaporin?

The channel protein that specifically allows water to undergo efficient facilitated diffusion across the plasma membrane

What does hypotonic mean?

Lower solute concentration

What does hypertonic mean?

Higher solute concentration

What does isotonic mean?

Equal solute concentration

How does water move in facilitated diffusion?

From areas that are hypotonic to areas that are hypertonic until solutions are isotonic

What happens if cells gain too much water?

They can burst open (-lyse)

What happens if cells lose too much water?

They can shrivel and die

What is active transport?

When a cell moves a solute against its concentration gradient (from low to high)

Does active transport require an energy input?

Yes

What do all mechanisms of active transport require?

Transport proteins & a source of energy

What do simple mechanisms use for energy?

ATP, moves solutes against concentration gradient

What do other mechanisms use for energy?

Cotransport → two solutes transported simultaneously

What do large molecules use to enter/exit the cell?

Vesicles

What is exocytosis?

Cell products leaving the Golgi Apparatus in membrane-bound vesicles, fusing with the plasma membrane, and emptying contents outside the cell

What cell products are exocytosed?

Signal molecules for cell to cell communication, secretory products, and glycosylated proteins

What is endocytosis?

When extracellular materials are engulfed by the plasma membrane

What is energy?

The capacity to cause change

What is kinetic energy?

The energy of movement

What is thermal energy?

The transfer energy in the form of heat

What is electromagnetic energy?

Energy within particles that move in waves

What is potential energy?

Non-moving energy

What is chemical energy?

Energy stored in chemical bonds

What does the First Law of Thermodynamics state?

Energy can be converted from one form to another, but not destroyed

What does the Second Law of Thermodynamics state?

Every energy transfer increases entropy in the universe

What is metabolism?

All chemical reactions that occur in our bodies

What happens in catabolic reactions?

Molecules are broken down, potential energy in chemical bonds is released and converted into other forms

Catabolic reactions are called ______, which means “energy-releasing":

Exergonic

Are energy inputs required for catabolic reactions?

No

What happens in anabolic reactions?

Cells must take energy from another source to convert into potential energy of new chemical bonds

Anabolic reactions are called ______, which means “energy-consuming”:

Endergonic

Are energy inputs required for anabolic reactions?

Yes

What is the role of activated carrier molecules?

Storage for energy from catabolic reactions, transfer energy into anabolic reactions

What are examples of activated carrier molecules?

ATP, NADH, & FADH2

What is the most important activated carrier molecule?

ATP

What is ATP made of?

Adenine, ribose, & 3 phosphate groups

What is ADP made of?

Adenine, ribose, & 2 phosphate groups

ATP is generated during ______ reactions.

Catabolic

ADP+P is generated during _____ reactions.

Anabolic

How is ATP used in anabolic reactions?

ATP donates its third phosphate group to the reactant, creating an unstable “phosphorylated intermediate” that can be replaced by a covalent bond.

How is ATP used in cellular work?

ATP donates its third phosphate to the desired protein, causing it to change shape to induce the desired changes and carry out cellular work

What are enzymes and what do they do?

Biological catalysts that cells use to increase the rate at which all kinds of metabolic reactions occur

What does the structure of enzymes include and what does it do?

A binding site for reactants that often include amino acids that can form hydrogen bonds with the substrate and reinforce binding

What allows enzymes to catalyze only one specific reaction?

Their unique tertiary shape

What must happen for any chemical reaction to occur?

Chemical bonds in reactants must become unstable

What is the unstable state of chemical bonds called?

Transition state

What do enzymes do to the activation energy in reactions?

Lowers it, makes it more likely that reactants will shift into transition state

How do enzymes increase the rate of a chemical reaction?

They bind both reactants in chemical reactions to bring them closer and promote their interaction or they slightly alter the shape of the substrate to shift it to the transition state

What is aerobic respiration?

The most important catabolic reactions for ATP production in our cells

What is the most important source of energy & initial substrate for aerobic respiration?

Glucose

What happens when energy is released rapidly in aerobic respiration?

Energy can be lost as heat

What is the goal of aerobic respiration?

To make as much ATP as possible

What are used as activated carrier molecules in aerobic respiration?

NADH + FADH2

How do NADH + FADH2 store energy?

In electrons

What are redox reactions?

Reactions that involve electron transfers

What does being “reduced” mean in redox reactions?

Molecules are gaining electrons and energy

What does being “oxidized” mean in redox reactions?

Molecules are losing electrons and energy

OiL RiG:

Oxidation is Loss, Reduction is Gain

NAD+ accepts electrons to become _______ .

NADH

FAD+ accepts electrons to become _______ .

FADH2

What is the first step of aerobic respiration?

Glycolysis

Where does glycolysis take place?

The cytoplasm

Does glycolysis require oxygen?

No

What is the reactant in glycolysis?

Glucose (6 carbons)

How many molecules of ATP must be consumed in glycolysis?

2

What are the products of glycolysis?

2 pyruvate (3 carbons), 4 ATP (2 Net ATP), 2 NADH

What is the second step of aerobic respiration?

Conversion of pyruvate to AcetylCoA

Where does the conversion of pyruvate to AcetylCoA take place?

The mitochondrial matrix

What are the reactants of the conversion of pyruvate to AcetylCoA?

2 pyruvate and 2 coenzyme A